Laughing gas unsafe, say doctors

May 5, 2005 — 10.00am

The nitrous oxide gas used in most general anaesthetics is unsafe and should be discontinued, according to Australian doctors who have found it doubles the rate of serious vomiting and pneumonia after surgery and raises the risk of wound infections.

Their world-first study of 2050 patients also showed patients who had undergone surgery were slower to recover and likely to stay in hospital longer if the gases used to keep them unconscious included nitrous oxide as a base, rather than oxygen or oxygen and air.

Paul Myles, the director of anaesthesia at The Alfred hospital, said: "This is going to really surprise people... nitrous oxide is used in 80 per cent of anaesthetics. It's the foundation of anaesthesia and has been that way for 160 years."

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Professor Myles, who led the 20-hospital international study, said he had already stopped using nitrous oxide in his own practice, though "it possibly has a role in simple surgery for young, healthy patients".

Because it changed the way the body metabolised vitamin B12 and folate, it was also possible nitrous oxide could cause immune system and heart problems, nerve damage, cancer and birth defects, Professor Myles said. Those potential effects, combined with those demonstrated by the study, spelled "the end of nitrous oxide" in general anaesthesia, he added. But it would still have a role in securing fast pain relief, such as after injury or while giving birth.

The preliminary results will be presented in Auckland on Saturday to the Annual Scientific Meeting of the Australian and New Zealand College of Anaesthetists.

Michael Cousins, the college's president, said a phasing-out of nitrous oxide would be good news for patients. "If we eliminate nitrous oxide from the equation, there will be a lot fewer people feeling very sick," he said.